Either load it with:
[ Metacello new
baseline: 'BookletDSst';
repository: 'github://massimo-nocentini/Booklet-DSst/src';
load ] on: MCMergeOrLoadWarning do: [:warning | warning load ]or depend on it with:
spec baseline: 'BookletDSst'
with: [ spec repository: 'github://massimo-nocentini/Booklet-DSst/src' ]